A polycarbonate resin is generally produced using bisphenols as a monomer ingredient and by making use of its superiority such as transparency, heat resistance and mechanical strength, is widely utilized as a so-called engineering plastic in the fields of electric•electronic parts, automotive parts, optical recording mediums, optics such as lens, and the like. However, in the application to an optical compensation film of, for example, a flat panel display that is rapidly spreading in recent years, higher optical characteristics such as low birefringence and low photoelastic coefficient are required, and the conventional polycarbonate resin using bisphenols as a monomer ingredient becomes incapable of meeting the requirement.
Also, the conventional polycarbonate resin is produced using a raw material derived from petroleum resources, but in recent years, depletion of petroleum resources is feared, and it is demanded to provide a polycarbonate resin using a raw material obtained from biomass resources such as plant. In addition, because of a concern that global warming due to increase or accumulation of carbon dioxide emissions may bring about climate change or the like, development of a polycarbonate resin using a plant-derived monomer as a raw material and being carbon neutral even when discarded after use is demanded.
Under these circumstances, a method for obtaining a polycarbonate resin by using, as a monomer ingredient, a special dihydroxy compound and allowing transesterification with a carbonic acid diester to proceed while removing a byproduct monohydroxy compound by distillation under reduced pressure, has been proposed (see, for example, Patent Documents 1 to 6).
The polycarbonate resin is required to be provided, before its formation into product pellets, with a performance according to the application of the final product, for example, by adding/dispersing a catalyst deactivator to stop the progress of polymerization, removing a volatile ingredient such as residual monomer under reduced pressure, or adding/dispersing an additive such as heat stabilizer and release agent, and in the case of the conventional polycarbonate resin using bisphenol A as a monomer ingredient, it has been proposed to perform such an operation by using an extruder (see, for example, Patent Document 7).